It is well known in the art that a typical RF power amplifier requires some type of hybrid to split and combine RF power because there are limits to the output power of a single transistor. A hybrid is a 3dB (equal power division) directional coupler. High-powered, push-pull transistors are used because such circuit allows the terminal impedances of the transistors to be connected in series for RF operation. These high powered transistors have a very low impedance and thus, special requirements must be met in order to match the push-pull transistors to input and output impedances. Thus, two elements are involved in the attempt to increase RF power output. The first element is a hybrid which splits the incoming RF power from a single input to two outputs which are isolated from each other. The difficulty occurs not in splitting the RF signals, but in splitting those signals such that they are isolated from each other which is a requirement for the hybrid. The other requirement is the need for a balun which performs a balanced-to-unbalanced (balun) impedance transformation. This is necessary because the input and output circuitry for balanced-transistor amplifiers must not only match the impedance of the device to that of the system in order to ensure proper efficiency, bandwidth and power transfer, but also must take an unbalanced input, referenced to ground, and create a balanced output comprised of two signals which are precisely 180.degree. out of phase.
The most common hybrid is the in-phase type, also known as the Wilkinson type, such as that disclosed in U.S. Pat. No. 4,309,666. Hybrids differ with respect to bandwidth, loss, phase and amplitude balance, cost and fabrication. Once a hybrid is chosen that suits the application, it must be cascaded with balun impedance transformers to match the input impedance of the push-pull transistors. Thus, the prior art requires a hybrid cascaded with the balun impedance transformers to enable RF power to be split, amplified and then recombined at a higher power level.